The present invention relates in general to electrosurgical treatment of tissue and, more particularly, to a method and apparatus for electrosurgical treatment wherein tissue impedance or tissue impedance in combination with tissue temperature are used to control the electrosurgical treatment.
Many available radio frequency (rf) generators for use in the medical field for surgical purposes including cauterization, dissection, transection, tissue welding and the like, generally do not effectively regulate the electrical power supplied to an electrosurgical instrument. Typically such generators control the voltage such that a selected power level is approximately delivered and a maximum power level is not exceeded. When such rf generators are used, the primary control is the experience of the surgeon who responds to what is observed as happening to the tissue being treated using the rf energy. Often, particularly for endoscopic procedures, surgeons can not see what is happening to the tissue and may not be able to react quickly enough even if good observation is possible.
A variety of instrument and rf energy generator control arrangements have been proposed. For example, temperature sensors have been incorporated into rf forceps to sense the temperatures of the contact faces of the forceps with the rf power applied to the forceps being controlled based on the temperature of one or both of the contact faces or the temperature difference between the contact faces.
Rf power has been controlled in accordance with the square of the impedance over the range of increasing tissue impedance. The differential quotient of tissue impedance has also been considered with regard to determining the initial power level and the time for switching off rf power applied to tissue.
Notwithstanding these control arrangements, there is a continuing need in the art for different approaches and techniques for the control of rf energy powered surgical instruments to better assist surgeons and improve treatment using rf energy.